Generally, magnetic recording tapes are used as audio tapes, video tapes and computer tapes. Due to the recent increased demand for high density recording, a ferromagnetic thin metal film type magnetic recording medium which is prepared by a vapor deposition method such as vacuum evaporation, sputtering or ion plating or plating such as electric plating or electroless plating as described in U.S. Pat. Nos. 4,002,546, 4,226,681, 4,354,908, etc., has drawn attention and has been put into practical use. The surface of the magnetic recording layer for magnetic recording tapes for audio, video or computer use is smoothed to improve sensitivity (i.e., particularly output in the high frequency region). However, a magnetic recording tape with a smooth surface tends to be wound unevenly upon winding and rewinding. Where such a tape is used, the running properties are decreased because of changes of tension and thus the output changes. Further, the tape tends to be deformed and to be damaged. A magnetic recording tape having a backing layer which is provided on the surface of a support opposite to the surface on which the magnetic recording layer is present has been proposed to eliminate the above defects as described in U.S. Pat. No. 4,367,261.
However, defects such as scraping away, increase in abrasion coefficient and tape damage with the conventionally used backing layer, and further improvement is desired.
Further, where a backing layer is provided to improve the running properties and running durability, it is known that the magnetic recording medium (particularly, in the form of a tape) has defects that where the magnetic recording medium is wound in a roll or is piled as sheets, the unevenness of the backing layer is transferred to the surface of the magnetic recording layer, the surface properties of the magnetic recording layer are deteroprated and the electromagnetic properties, particularly S/N characteristic of the magnetic recording medium, are degraded.
There are serious defects in a metal thin film type magnetic recording medium, for example, (1) abrasion resistance toward the magnetic head or guide pole upon recording, reproducing and erasing signals is high, and therefore wear resistance decreases and (2) the abrasion coefficient toward tape guiding systems for magnetic tapes to run is large because a smooth support is used for high density and high S/N recording, and therefore the running is unstable. Specifically, a high degree of jitter occurs while the tape is running.